/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.index.mapper;

import org.apache.lucene.document.Field;
import org.apache.lucene.document.NumericDocValuesField;
import org.apache.lucene.search.Query;
import org.opensearch.index.mapper.ParseContext.Document;
import org.opensearch.index.query.QueryShardContext;
import org.opensearch.index.query.QueryShardException;
import org.opensearch.search.lookup.SearchLookup;

import java.util.Collections;

/**
 * Mapper for the _version field.
 *
 * @opensearch.internal
 */
public class VersionFieldMapper extends MetadataFieldMapper {

    public static final String NAME = "_version";
    public static final String CONTENT_TYPE = "_version";

    public static final TypeParser PARSER = new FixedTypeParser(c -> new VersionFieldMapper());

    /**
     * Field type for internal version field
     *
     * @opensearch.internal
     */
    static final class VersionFieldType extends MappedFieldType {

        public static final VersionFieldType INSTANCE = new VersionFieldType();

        private VersionFieldType() {
            super(NAME, false, false, true, TextSearchInfo.SIMPLE_MATCH_ONLY, Collections.emptyMap());
        }

        @Override
        public String typeName() {
            return CONTENT_TYPE;
        }

        @Override
        public Query termQuery(Object value, QueryShardContext context) {
            throw new QueryShardException(context, "The _version field is not searchable");
        }

        @Override
        public ValueFetcher valueFetcher(QueryShardContext context, SearchLookup lookup, String format) {
            throw new UnsupportedOperationException("Cannot fetch values for internal field [" + name() + "].");
        }
    }

    private VersionFieldMapper() {
        super(VersionFieldType.INSTANCE);
    }

    @Override
    public void preParse(ParseContext context) {
        // see InternalEngine.updateVersion to see where the real version value is set
        final Field version = new NumericDocValuesField(NAME, -1L);
        context.version(version);
        context.doc().add(version);
    }

    @Override
    public void postParse(ParseContext context) {
        // In the case of nested docs, let's fill nested docs with version=1 so that Lucene doesn't write a Bitset for documents
        // that don't have the field. This is consistent with the default value for efficiency.
        Field version = context.version();
        assert version != null;
        for (Document doc : context.nonRootDocuments()) {
            doc.add(version);
        }
    }

    @Override
    protected String contentType() {
        return CONTENT_TYPE;
    }
}
